1. Field of the Invention
The present invention relates to an ultraviolet resistant object or article having at least a portion made of a polymer material and having a resistance to ultraviolet light, as well as a method of manufacturing the same.
2. Description of the Background Art
Polymer materials such as resin and rubber have been used in various fields owing to their light weights and high shock resistances. However, the polymer materials generally have low resistance against ultraviolet light, and are liable to be deteriorated when irradiated with ultraviolet light. Accordingly, significant deterioration of a portion made of the polymer material is liable to occur in such a case that the polymer material portion is present in a device, instrument or the like, which is used near an ultraviolet lamp in a hospital, laboratory or the like, or in an outdoor position or the like exposed to sunlight. In particular, objects for a medical use are usually kept in environments where they are irradiated with ultraviolet light in many cases, although they are usually sterilized by a high-pressure steam, a gas or the like before use.
In order to suppress deterioration of the polymer material due to exposure to ultraviolet light, various methods have been employed. For example, an ultraviolet absorbent is kneaded into the polymer material, or a coating material containing an ultraviolet absorbent is applied to the surface of the portion made of polymer material.
For example, Japanese Laid-Open Patent Publication No. 8-98870 (98870/1996) has disclosed that an ultraviolet shielding container for a medical use, which is made of a thermoplastic resin additionally containing 0.01-1%, by weight, of titanium oxide having an average particle diameter of 10-40 .mu.m, can prevent change in quality of contents in the container due to ultraviolet irradiation while maintaining a transparency of the resin.
According to the method in which the ultraviolet absorbent is kneaded into the polymer material, however, addition of the ultraviolet absorbent may change original characteristics such as a mechanical strength and a thermal resistance of the polymer material. In some cases, this method cannot be applied to medical objects and others without difficulty because the ultraviolet absorbent may impair safety of human bodies.
According to the method in which a coating material including the ultraviolet absorbent is applied onto the object, the original characteristics of the polymer material are hardly affected in many cases. However, increase in amount of the ultraviolet absorbent lowers the adhesivity of the coating material to the polymer material so that the amount or content of ultraviolet absorbent is restricted. Accordingly, the ultraviolet shielding performance cannot be sufficiently achieved. Further, the coating material inherently has a low adhesivity to the polymer material, and therefore a possibility of peeling off increases over time. For these reasons, it is difficult to keep an intended ultraviolet absorbing performance for a long term. Moreover, even an object employing the coating material may not be applied to a medical object or the like, depending on the safety achieved by the ultraviolet absorbent.